This proposal incorporates a phased career development plan for a candidate with a long-standing interest in research and basic investigation skills. Under this phased plan, the first two years of training will incorporate methods development, preliminary experimentation, and didactic course-work selected to build on the candidate's background in clinical veterinary medicine. The following two years will be spent using the previously developed methods to intensively investigate aspects of bacterial infection of the central nervous system (CNS). The candidate will develop an in-vitro primary cell culture system to serve as a model for infection of the vasculature at the level of the blood-brain barrier. The system will be used to investigate the pathogenesis of a bovine CNS pathogen, Haemophilus somnus, (H. somnus). This pathogenic bacterium will serve as a model for infection at the blood-brain barrier by related human CNS pathogens that are difficult to study as a result of host-restriction. The blood-brain barrier protects the brain parenchyma from foreign agents and inflammatory mediators and aids in the regulation of intravascular coagulation. The endothelial cell is the central cellular constituent of the blood-brain barrier. This project will focus on the role of the cerebral microvascular endothelial cell (CMVEC) in H. somnus cerebrovascular pathology. H. somnus infection can result in an acute neurological disease, pathologically similar to meningococcemia, characterized by a fibrinopurulent meningitis, haemorrhage with abscessation and a thrombotic vasculitis of the CNS. We will specifically investigate the interactions of H. somnus with the CMVEC relative to alterations in endothelial cell derived mediators of intravascular coagulation and inflammation, the role of the cytoskeleton in regulating vascular permeability, and apoptosis. Determining the mechanisms involved in destruction of the blood-brain barrier and localized coagulation in the CNS as a result of H. somnus infection could elucidate common pathogenic mechanisms used by other neurotropic bacteria, (i.e. Neisseria meningitides) to invade the CNS. Completion of this research project will also provide the candidate with the means to further build on her current research techniques and cognitive abilities, and acquire new technical laboratory skills that will assist in the candidate's progression to independence as a scientist.